1. Field of the Invention
This invention relates to improvements in multifilament yarns formed from high tenacity polyolefin fibers.
2. Description of the Related Art
It is extremely difficult to provide yarns formed from high tenacity fibers with long-lasting color. These yarns may be formed from high tenacity polyolefin fibers, such as high tenacity polyethylene fibers. These fibers are available from Honeywell International Inc. as SPECTRA® extended chain polyethylene fibers, and they are also available from other suppliers.
Typically, such high tenacity fibers are made by a spinning a solution containing polyethylene gel swelled with a suitable solvent into filaments of ultrahigh molecular weight polyethylene. The solvent is removed and the resulting yarn is stretched or drawn in one or more stages. In general, such filaments are known as “gel spun” polyolefins, with gel spun polyethylene being the most commercially sold. Solution spun polyolefin fibers are also known, as are melt extruded fibers.
Typically, the multifilament high tenacity yarns require a surface treatment step prior to applying a colorant. For example, these yarns may be treated by plasma spray or corona treated and then immediately followed with the application of a colored coating. However, such colored coating tends to come off with vigorous rubbing.
Preparation of monofilament-like fishing lines from gel spun polyethylene fibers are disclosed, for example, in U.S. Pat. No. 6,148,597 and in WO 2006/040191 A1. In these disclosures multifilament yarns are processed such that the filaments are fused together to yield a monofilament-like line.
It would be desirable to provide multifilament high tenacity yarns that have improved color-fastness.